Day: September 7, 2013

Treadmills can often be found on the side of the road, after someone gave up on their running regimen and found that the machine was taking up too much space in their basement. This is great for hackers, since they have some useful parts in them.

However, if you’d like to actually use a treadmill for running, some entertainment would certainly help. [KingJackOff] decided to roll his own treadmill entertainment system out of things he had lying around, bringing the total cost to $0.

He took an old laptop and mounted it in a piece of rigid foam using a gratuitous amount of duct tape. With the screen and keyboard mounted, he added speakers and a slot for the DVD drive. Then a printed graphic was taped to the front, with a nice motivational message.

Lots of people have old laptops lying around with mechanical issues. Broken hinges and frames make them unusable, even though the electronics are fine. Some foam and paper could be all you need to bring one back to life.

The security of the system depends on xscreensaver, which has a password protected lock feature already built into it. When the tag is removed from the reader’s field it fires up the screensaver using a Perl script.

But waking up from the screensaver is a bit more tricky. The package doesn’t allow you to wake it from the command line — most likely for security. He found the xdotool to be of great use here. It is a command line tool which simulates keyboard and mouse entry. His script detects when the xscreensaver password prompt is on the screen and uses the xdotool to fill in [Kristoffer’s] password. Since the script knows what has focus it won’t give away your password by accident.

The 2013 Open Hardware Summit took place on September 6th at MIT. There was a wide array of demos and talks covering Open Hardware methodologies and projects. After the break I’ll be covering the demo area of the conference, and sharing some of my favorite demos.

Fast and accurate is a good description of this laser engraver built by [Ragnar] and [Gunnar]. The’re planning to show it off at the Trondheim Maker Faire after the new year but they took it out in the wild for the PSTEREO Mini Maker Faire (also in Trondheim) this past August. The video below gives an overview of the build process and the engraver at work. But we also enjoyed reading the post about a few missteps in the early prototyping process. We call this one a proper laser engraver because it was purpose built from the ground-up. We still like seeing the engravers hacked from optical drives, but this really is a horse of a different color in comparison.

From the start they’re using familiar parts when it comes to CNC builds. The outer frame is made of extruded aluminum rail, with precision rod for the gantry to slide upon. Movement is facilitated with stepper motors and toothed belts, with all of the connecting and mounting parts fabricated on a 3D printer. The mistake made with an early (and unfortunately mostly assembled) prototype was that the Y axis was only driven on one side when it really needed to be driven on both. But filament is relatively cheap so a few tweaks to the design were able to fix this and get the production back on track.

To the upper right we have very pure potassium chlorate, so much so that it bursts into flames when mixed with sugar and catalyzed with some sulfuric acid. [Mr. Home Scientist] produced the KClO3 using household chemicals and some rudimentary equipment sourced on eBay.

The experiment started off with concentrated bleach containing 8.25% sodium hypochlorite. He needed sodium chlorate so a hot plate was used to boil the bleach until crystals started to form. A more efficient way to achieve this reaction would be using electrolysis (check out the HHO generator we saw recently for a homemade rig). The next step is to add potassium chloride, which is sourced from the grocery store as a sodium-free salt alternative. After mixing with the filtered remains of the bleach reaction the two are combined. There is no precipitate from this — an indication that not everything is as it should be. But an overnight stay in the refrigerator results in the potassium chlorate crystals seen above.

This pair of dongles is a fun way to get your feet wet working with MIDI hardware. They’re called MIDIvampire-I and MIDIvampire-II. Just plug one end into your MIDI-ready instrument and the other into a pair of speakers and you’re off and running. Mark I is a polyphonic synth, and Mark II is a drum machine, but both use basically the same hardware which you may already have on hand.

The single chip on each board is an ATmega328 often found anchoring Arduino boards. The other silicon component is an S1112B30MC voltage regulator. The rest of the components are passives, with MIDI and headphone jacks for connectivity. They’re selling these if you want the easy way out, but we thought we’d bring them to your attention in case you needed a breadboarding project this weekend. The firmware, BOM, schematic, and board artwork are all available on the Wiki pages linked in the articles above. After the break you can see a couple of demo videos which walk through all of the features.